A year ago Mr Jiang unveiled his "eight-point plan" for union with Taiwan. By Peking standards, it was conciliatory: "We should strive for the peaceful reunification of the motherland since Chinese should not fight Chinese," he declared.
Twelve months on, China is threatening the peace of the Far East, and conceivably the world, by brandishing harsh words and military manoeuvres against the large, stubborn island off its eastern shore. What went wrong? From the Chinese president's viewpoint, a lot.
In his New Year speech last year, Mr Jiang was, in effect, pinning his reputation on a successful handling of the "Taiwan question" - aspiring, in the process, to strengthen his position as heir apparent to the ailing 91-year-old patriarch, Deng Xiaoping.
Reunification with Taiwan had always been Deng's great goal. In the early Eighties, he made overtures to establish a relationship with Taipei. The "one country, two systems" proposal - which has provided the framework for the return of Hong Kong in June 1997 - was originally devised by Deng for Taiwan, the only part of the old Chinese empire to remain under nationalist, that is anti-Communist, control when the civil war ended in 1948.
Deng was opposed to the use of force against Taiwan. As a veteran Long March commander, he had the clout to restrain the People's Liberation Army (PLA) top brass. In grasping the challenge of Taiwan, Mr Jiang was saying, as clearly as Chinese leaders say anything, that he was capable of leading China.
As President, Communist Party chief and head of the armed forces (more titles than Deng ever had), he should not have been feeling insecure. But titles are not enough to bestow true authority in Chinese politics. Despite being Mr Deng's anointed heir, Mr Jiang's pedigree has never looked that impressive .
The eight-point plan for Taiwan was always a risk; from Peking's viewpoint it has become a disaster. It has, in effect, been thrown back in Jiang's face by Taiwan's president, Lee Teng-hui. While stopping short of calling for independence - a sure-fire invitation to invasion - he has infuriated Peking by demanding greater international recognition of Taiwan's status as an economic power in its own right.
From the start, the Chinese generals were not pleased by Mr Jiang's relatively mild tone. When President Lee obtained a US visa for a university reunion last June, the army chiefs were incandescent. No Taiwanese president had visited the US since the Peking-Washington detente of the 1970s. In the view of Peking's military hardliners, a US visit, even a private one, was an assertion of de facto Taiwanese independence.
Last summer, stories did the rounds in Peking about how Mr Jiang had been called to account by the generals for his mis-handling of the Taiwan issue and told to adopt a tougher stance. By early July, the PLA had started exercises off the coast of Zhejiang, eastern China. By the end of that month, the PLA had tested surface-to-surface guided missiles off the northern tip of Taiwan.
For two years, President Jiang has been courting the army top brass by, among other things, agreeing large military budget increases. By last summer, those efforts were in danger of being swept away. Not having the authority to tell the generals to back off, there was only one option. Mr Jiang changed his tone.
The PLA continued with its planned exercises, with his support. In August the war games, including amphibious landings, restarted on the Fujian coast, opposite Taiwan, and more missile and artillery firings in the East China Sea. November brought a large scale amphibious landing exercise on Dongshan Island, in southern Fujian.
Official media reports featured Mr Jiang inspecting the troops and watching the exercises, in images deliberately reminiscent of Chairman Mao. Notice was given that further large-scale exercises were planned in the run-up to the 23 March Taiwan elections - a blatant attempt to scare the islanders into voting for anyone but Lee. China has also repeated its scarcely veiled warnings that any step towards independence would bring a military response.
In a telling statement Mr Jiang last month declared: "We cannot sacrifice culture and ideology for a short period of economic development." In other words, politics must regain the ground lost to pragmatism under Deng's economic reform programme.
The pre-eminence of politics is a message he is now urgently concerned to impress on the army. On a much publicised visit to the Liberation Army Daily, he was again quoting Mao ("newspapers must be run by statesmen"), but also trying to reassert his authority over the military. "Senior officers must attach the utmost importance to politics and must be clear-minded on political issues."
During next Sunday's Lunar New Year broadcast, Mr Jiang will again heap praise on the armed forces. To China-watchers, this preoccupation with the army suggests he is far from sure he has control over his commanders. Outright military action against Taiwan seems unlikely; but belligerent exercises hold obvious dangers of accidental escalation.
It is now two years since Deng was seen in public. No one had expected him to survive this long. The longer he lasts, the better positioned Mr Jiang, his chosen successor, will be. The Chinese president must be hoping that the Year of the Rat, a prosperous sign in the Chinese calender, bodes well for an old man's health. From the point of view of Taiwan, Asia, and the rest of the world, it is also better if the old man hangs on a while. Uncertainty is bad for the nerves; but a disputed succession, with the military flexing its muscle, might be even more alarming.Reuse content